1. Field of the Invention
This invention relates to a key support device for rotatably supporting keys used in electronic keyboard instruments, such as electronic pianos and electronic organs.
2. Prior Art
A keyboard support device of this kind includes a type which supports rear portions of keys by support members provided on a keyboard chassis. This type of keyboard device is disclosed e.g. in Japanese Patent Publication (Kokoku) No. 3-30875 and Japanese Patent Publication (Kokoku) No. 45-8828.
Japanese Patent Publication (Kokoku) No. 3-30875 discloses:
(1) a key support device constituted by holes punched through part of a keyboard chassis made of metal, and engaging recesses formed in rear ends of keys for direct engagement with the inner peripheral edges of corresponding ones of the holes, respectively, thereby supporting the keys each on the fulcrum of the inner peripheral edge of a corresponding one of the holes, and
(2) a key support device constituted by a cylindrical support shaft made of resin mounted on a keyboard chassis, and a shaft-receiving hole formed circular in cross-section through a rear end of each key for engagement with the cylindrical support shaft, thereby supporting each key on the shaft.
Japanese Patent Publication (Kokoku) No. 45-83828 discloses:
(3) a key support device constituted by a support shaft integrally formed with a keyboard chassis, which is semicircular in dross-section, and a recess defined between a pair of tapered sloping walls formed at a rear end of each key for engagement with the support shaft, thereby supporting each key on the support shaft.
However, the key support device (1) has a drawback that keys are liable to wear, because the inner peripheral edge of each hole formed through the keyboard chassis made of metal is in direct engagement with the engaging recess of each key, which results in a degraded durability of the key support device, and noise is ready to occur.
The key support device (2) is free from the drawback of the key support device (1), because the shaft-receiving hole, circular in cross-section, of each key is engaged with the cylindrical support shaft made of resin. However, not only the material cost is increased due to the resin used for forming the support shaft, but also the assembly work cost is increased due to time required in mounting the support shaft on the keyboard chassis.
Further, the key support device (3), in which the support shaft, semi-circular in cross-section, and the recess, formed by the tapered sloping walls of the key, are engaged with each other, is liable to suffer from looseness or eccentric wear of contact surfaces of these component parts.